1 / 59

Cellular Structure & Function

Cellular Structure & Function. Part 1: Organization of the Human Body. The Cell. Building block of the all organisms, from single-celled to human. 200 Types of cells in the human body, categorized by cell shape. Cell size limited by the volume and surface area ratio.

changw
Download Presentation

Cellular Structure & Function

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Cellular Structure & Function Part 1: Organization of the Human Body

  2. The Cell • Building block of the all organisms, from single-celled to human. • 200 Types of cells in the human body, categorized by cell shape. • Cell size limited by the volume and surface area ratio. • If the cell is too big, it cannot support itself or absorb nutrients/excrete wastes effeciently.

  3. Classes of Cell Shapes • Squamous: Thin & flat cells covering surfaces or lining “tubes” • Example: Skin, lining of the esophagus • Cuboidal: Square or cube shaped; approximately as wide as they are tall. • Example: Liver cells • Columnar: Much taller than they are wide. • Example: Lining of the intestines • Spheroid: Egg cells and fat cells; round or oval. • Fusiform: Thick in the middle and tapered towards the ends. • Example: Smooth muscle cells • Stellate: Star-shaped cells. • Example: Some nerve cells

  4. Cell Theory • Based on Robert Hook, Theordore Schwann, & Louis Pasteur • Modern Cell Theories’ Generalizations: • All organisms are composed of cells and cell products. • The cell is the simplest structural and functional unit of life. • All functions and structures are ultimately due to the activities of cells. • Cells come only from pre-existing cells. • The cells of all species have many fundamental similarities.

  5. General Cell Structure • Cells have the following general structures: • Cell Membrane • Cytoplasm • Nucleus • Intracellular Organelles

  6. Cell Membrane • All cells are surrounded by a plasma membrane made up of proteins and lipids • Composition and function differ from one area of the body to the other. • Bilayer of lipids with diverse proteins embedded in it • 98% of membrane molecules are lipids • 75% of these are phospholipids

  7. Cell Membrane • Phospholipid Bilayer: • Two phospholipid layers thick • Hydrophilic heads facing the water on each side of the cell membrane. • Hydrophobic tails directed toward the center of the membrane (avoiding the water) • Membrane is dynamic and “fluid”

  8. Cell Membrane • Cell Membrane is the target site of many pharmaceutical agents • Proteins only make up 2% of the molecules in a plasma membrane, but are larger then lipids and make up around 50% of the membrane weight.

  9. Cell Membranes • Integral or Transmembrane Proteins: Pass across the plasma membrane and are responsible for many functions. Integral proteins function as… • Receptors: Specific for one messenger • Second-messenger Systems: Triggered by messengers that bind with surface receptors • Enzymes: Produce second messengers and help with digestion in the small intestine • Channel Proteins: These molecules have “pores” & allow passage of water & other solutes through the membrane • Carriers: Also called “PUMPS” they actively transport molecules into the cell utilizing ATP in the process

  10. Glycocalyx • The “fuzzy” coat external to the plasma membrane on all animal cells, including humans • Acts as an “identification” tag that enables the body to distinguish its own healthy cells from transplanted tissue, invading organism, and diseased cells.

  11. Surface Extensions • Surface extensions aid in absorption, movement, and sensory processes. • Microvilli: Extensions of the plasma membrane; serve primarily to increase a cell’s surface area; best developed in cells that specialized in absorption (e.g. the cells lining the small intestine)

  12. Surface Extensions • Cilia: Multiple hair-like processes that project from the surface of the cell • Nonmotile Primary Cilium: Nearly every human cell has a single nonmotile primary cilium. • Play a role in balance in the inner ear. • Motile Cilia: Less widespread but occur widely in respiratory tract and fallopian tubes; “wave” to help move materials through internal tubes

  13. Surface Extensions • Flagella: A single whip-like structure much longer than cilia. • The only functional flagellum in humans is the tail of the sperm cell.

  14. Cytoplasm • Cytoplasm: The fluid that is contained inside the plasma membrane. • Crowded with fibers, tubules, passageways, and compartments. • Contains cytoskeleton (supportive framework) and intracellular organelles embedded in the cytosol or Intracellular fluid (ICF). • Extracellular fluid (ECF) is the fluid outside the cell.

  15. Nucleus • Nucleus: The structure at the center of the cell containing the genetic information for the organism. • Nucleic Acid: DNA or RNA. • DNA is the principle type of nucleic acid contained in the cell nucleus. • DNA contains the genetic code for organisms and is involved in protein synthesis, cell division (mitosis), and reproduction of the organism.

  16. Plasma Membrane • Plasma Membrane: Acts as a barrier and gateway between the cytoplasm and the extracellular fluid. • Selectively Semi-Permeable: The plasma membrane lets some things through and blocks other things; this is tremendously important in clinical practice!

  17. Plasma Membrane • Methods of Transporting Substances: Passive and Active transport. • Passive Transport includes… • Filtration • Diffusion • Osmosis • Active Transport requires ATP and includes… • Active transport • Vesicular transport

  18. Filtration • Filtration: The process by which particles are driven through a filter, or selectively permeable membrane, via hydrostatic pressure exerted on a membrane by water. • Example: Coffee Filter • Weight of water forces water through the grounds and coffee filter. • Filter holds back the larger particles (coffee grounds) • Most important filtration in the human body occurs in the capillary wall – transfer of water, salts, nutrients, etc. from blood stream to tissue and extracellular fluid & wastes to kidneys

  19. Simple Diffusion • Simple Diffusion: The net movement of particles from an area of higher concentration to an area of lower concentration. • The result of constant, spontaneous movement of molecules known as Brownian Movement. • Concentration Gradient: When the concentration of a substance differs from one point to another. • Movement occurring down or with the concentration gradient is movement from the higher concentration area to the lower.

  20. Simple Diffusion • IF the membrane is semi-permeable and permeable to that substance, than diffusion will occur. • IF the membrane is not permeable to the substance, it will not diffuse across the membrane.

  21. Diffusion Rates • Diffusion Rates: Important to cell survival because they determine how quickly a cell can acquire nutrients or rid itself of wastes. • Factors affecting diffusion rate: • Temperature: The higher the temp, the faster the diffusion rate. • Molecular Weight: Heavy molecules diffuse more slowly. • Membrane Surface Area: The more surface area the faster the diffusion rate. • “Steepness” Of Concentration Gradient: The greater the concentration difference, the faster the diffusion. • Membrane Permeability: The permeability of the membrane. • Diffusion Distance: Distance diffusion occurs across. • Facilitated Diffusion: Whether a solute binds to a specific transporter (changes the shape and releases the solute on the other side of the membrane).

  22. Osmosis • Osmosis: The diffusion of water through a selectively permeable membrane from the area of higher water concentration to the area of lower water concentration. • The higher solvent (water) concentration area has a low solute concentration. • The higher solute concentration has a low solvent concentration.

  23. Tonicity • Tonicity: The ability of a solution to affect the fluid volume and the pressure in a cell. • If a solute cannot pass through a plasma membrane, but remains more concentrated on one side of the membrane than on the other, it triggers osmosis.

  24. Tonicity • Hypotonic Solution: Area surrounding a cell has a lower concentration of nonpermeating solutes than the intracellular fluid. • Cells absorb water, swell, and lyse (burst). • Hypertonic Solution: Area surrounding cell has a higher concentration of nonpermeating solutes than the intracellular fluid. • Cells will lose water and crenate (shrivel). • Isotonic Solution: The area surrounding the cell has the same total concentration of nonpermeating solutes as the intracellular fluid. • Cells will neither loose nor gain water molecules & do not change size or shape.

  25. Active Transport • Active Transport: The carrier-mediated transport of a solute through a plasma membrane but against a concentration gradient. • Utilizes ATP and energy to move against the normal concentration gradient from an area of low concentration to high concentration. • Example: The sodium-potassium pump.

  26. Sodium-Potassium Pump • Used to regulate the balance of sodium and potassium within the cell. • 1 ATP molecule exchanges 3 sodium atoms (Na+) for 2 potassium (K+) atoms. • Keeps the potassium higher and sodium lower within the cell. • Plasma membrane continuously leaks Na+ and K+, so the pump keeps the balance corrected. • Na+ and K+ play a critical part in nerve impulses and cardiac function.

  27. Vesicular Transport • Vesicular transport moves large particles and droplets of fluid or numerous molecules through the plasma membrane all at once. • Endocytosis: Vesicular processes that bring matter into the cell. Two types: • Phagocytosis: “Cell eating” where foreign particles are engulfed (e.g. monocytes) • Pinocytosis: “Cell drinking” where droplets of extracellular fluid containing molecules used by cells are taken in. • Exocytosis: Vesicular processes that release matter from the cell.

  28. Organelles • Organelles: The internal structures within a cell that carry out specific functions. • Some are surrounded by one or two layers of a unit membrane and are therefore referred to as “membranous organelles.” • Membranous Organelles: Nucleus, mitochondria, lysosomes, endoplasmic reticulum, golgi complex. • Non-Membranous Organelles: Ribosomes, centrosome, centrioles, basal bodies.

  29. Membranous Organelles: Nucleus • Nucleus: The largest organelle, spheroid in shape. • Most cells have a single nucleus • Skeletalmuscle cells have multiple nuclei • Mature red blood cells are anuclear – have no nucleus. • Liver cells are multinuclear • Nucleus surrounded by nuclear envelope or membrane • Nucleoplasm: The material contained within the nucleus. • Includes… • Chromatin (DNA and protein) • Nucleoli (produces ribosomes)

  30. Membranous Organelles: Endoplasmic Reticulum (ER) • Endoplasmic Reticulum: “Little network within the cytoplasm” • A system of interconnected channels that extend through the cytoplasm and reach the nuclear membrane. • Channels called Cisternae • Two Types: • Rough Endoplasmic Reticulum: Channels are covered with ribosomes (synthesize proteins). • Smooth Endoplasmic Reticulum: Extends from the Rough ER to form membranous tubules network.

  31. Membranous Organelles: Endoplasmic Reticulum (ER) • Smooth ER synthesizes steroids & lipids • Rough ER is responsible for detoxifying alcohol and other drugs • Rough ER most abundant in cells that produce large amounts of proteins – such as those in the digestive glands • Skeletal and cardiac muscle contain extensive networks of smooth ER that store and release calcium to trigger muscle contraction.

  32. Membranous Organelles: Golgi Complex • Golgi Complex: The small system of cisternae which synthesize carbohydrates and put the finishing touches on protein and glycoprotein synthesis. • Primary function is to package protein into membrane-bound golgi vesicles • Some become secretory vesicles and store cell products such as breast milk & digestive enzymes • Some of these can become lysosomes

  33. Membranous Organelles: Lysosomes • Lysosomes: A package of enzymes which are bounded by a single unit membrane – usually produced by the Golgi complex • Primary function is to hydrolyze or digest proteins, nucleic acids, complex carbohydrates, and phospholipids • Autophagy: The digestion of surplus cells by their own lysosomal enzymes (as in the liver).

  34. Membranous Organelles: Peroxisomes • Peroxisomes: Resemble lysosomes but are smaller and contain different enzymes (oxidase) and are not produced by the Golgi Complex\

  35. Membranous Organelles: Mitochondria • Mitochondria: Organelles specialized for synthesizing ATP • Power-house of cells • Bean shaped • Outer and inner membranes • Generate most of the cell’s ATP • Cristae contain enzymes for aerobic respiration • Matrix enclosed in the inner membrane; site of oxidation of organic molecules; contains DNA and ribosomes.

More Related